In recent years, for the protection and cure of wound, bedsore, burn ulcer, donor site and the like of human skin, dressing agents having various functions have been developed. Dressing agents are individually packaged and then sterilized to prevent the skin from being infected with bacteria. This packaging has an important role of ensuring high sterility.
As a means of administering a drug to living organisms, a method for transdermal absorption of the drug through the skin, which comprises adhering an adhesive preparation containing a drug to a living organism, has been developed. Such a drug-containing adhesive preparation comprises a support made of a plastic film of polyester, polyethylene and the like, or a non-woven fabric, and an adhesive layer containing a transdermally absorbable drug, which is laminated on one surface of the support, wherein the exposed surface of the adhesive layer is covered with a coating material. Generally, such a drug-containing adhesive preparation is individually packaged with a packaging film for the purpose of preventing volatilization of the contained drug and/or influence of humidity, oxygen and the like (decomposition, oxidation and the like).
In general, individual packaging is performed by heat-sealing the packaging film surrounding the adhesive preparation by a packaging machine.
For the packaging film, various films impermeable or hardly permeable to humidity and oxygen have been developed. Depending on the kind of the packaging film and packaging methods, however, the heat-sealing treatment may not be sufficient, and a pinhole sometimes occurs. Occurrence of pinholes in the heat-sealed portion includes such occurrence due to an excessive pressure and heat applied for heat blocking for a heat sealing treatment, which causes breakage of a part of a packaging film, such occurrence due to an insufficient pressure and heat for the heat block, which makes the heat sealing treatment incomplete to allow pinholes, such occurrence due to wrinkles in the heat-sealed portion and the like. Moreover, since packaging films have inconsistent thicknesses, which in turn causes variation in the heat-sealing pressure on the heat-sealed portion, an effect of the tension on the packaging film becomes greater to permit easy development of the wrinkles. As a result, a pinhole easily occurs.
The band width of the heat-sealed portion is conventionally about 3 mm to 8 mm or above. To perform a heat sealing treatment free of occurrence of a pinhole by simultaneously and uniformly pressing a packaging film, while forming a heat-sealed portion with such a band width, control of special machines, determination of material and thickness of the packaging film and the like were necessary. Particularly, determination of the material and thickness of the packaging film is essential for avoiding the occurrence of pinholes. For packaging without a pinhole, a heat sealing resin capable of adhering at a low temperature is often used as a material of a packaging film, and in this case, the thickness of a packaging film tends to be greater.
When a transdermal absorption type adhesive preparation containing a drug is packaged, since the drug adsorbs to a heat sealable resin during preservation, the drug content of the adhesive preparation decreases, thus affecting the treatment effect. As a material of the packaging film, therefore, a heat sealable resin hardly adsorbable for drugs needs to be used. Moreover, to reduce the amount of the drug adsorbed to the packaging film as a whole, the thickness also needs to be made small. A heat sealable resin hardly adsorbable for drugs tends to require a higher heat sealing treatment temperature. In addition, when the thickness of the packaging film is reduced, the pressure for the heat sealing treatment tends to be non-uniformly applied to the entire portion of a packaging film to be heat sealing-treated. As a result, a pinhole easily occurs.
Conventionally, as the above-mentioned heat-sealed portion, an embossed heat-sealed portion (heat-sealed portion having a pattern of concave-convex, for example, tatami-matting weave-like dots, lattice and the like) has been employed. Therefore, minute pinholes are difficult to find by a nondestructive test such as an appearance test and the like. Accordingly, minute pinholes can only be found by a method including destruction of heat-sealed portion and the like, and the method is also problematic in view of the assurance of quality.